For decades, toys and displays have employed motion between slits, screens, and images behind them. Since the 1930s, advertising displays have used continuous belts of alternating clear and black lines, scrolling in front of back-lighted, interleaved images. Pop-up greeting cards and books have displayed images, which are pulled through openings to be revealed as the card or book is opened. Post cards printed with a lenticular image are made with an overlaying clear sheet with black lines attached by an eyelet, such that when the clear sheet is swivelled, the image underneath appears to move. Regarding lenticular imaging, the concept of creating image change, and film-type animation, by relative motion between the print and overlaying screen is well known in the art. However, it is useless without making adequate provisions for several accompanying concepts, vital to accomplishing this relative print-screen motion in a truly effective manner. Previous art has ignored some or all of these concepts, which are: (1) proper choice of whether to move a print or screen element, since it is not equivalent to move either, as certain conditions prohibit, or enhance motion of one or the other; (2) co-planarity of print and screen, which in most cases necessitates close contact between the entire area of print and overlaying screen; (3) mechanical advantage through a user-friendly interface, for precise, even, movement of screen or print; (4) ease of image replacement; (5) end user printing option and low cost software for mastering and printing of lenticular images with widely available computers and printers, as well as a file format which includes pertinent information to a lenticular file, such as lenses per inch, and number of compressed images; (6) accommodation of standard computer printer media sizes for consumer-printed images, such as index cards, or letter size; (7) reduction of friction between print and screen, even for user-printed images; and (8) option of adjusting co-linearity between print and screen.
Simply to prescribe sliding a print or screen to obtain an effect of motion, while not paying close attention to the above criteria, will result in a device incapable of a truly effective and practical display.
Close contact between the entire surface of the print and overlaying screen is necessary for very sharp focus, as simply placing a print against a lenticular screen will still show flatness discrepancies between their two planes as blurry areas. A rigid screen is needed to apply enough pressure against the print and its backing, and blurry areas still show up, due to lack of adequate contact between print and screen since, if the image and screen are gripped at their edges, their centers tend to bow away from each other. Because of reflections, it is not practical to apply pressure with an additional, rigid piece of clear plastic in front of the lenticular screen, unless backlighted.
U.S. Pat. No. 5,695,346 to Sekiguchi, shows a barrier or lenticular lens screen attached, in a first case near to, and in a second case, slightly farther from the hinged edge of the opening flap of a greeting card. The first case does not provide for proper screen trajectory, and the second case, because of the distance between print and screen, is not practical for the use of anything but a barrier strip, which suffers from lack of adequate light. The first case also, in which a lenticular screen moves over the print, is self-defeating, since greeting cards are usually opened by grasping the back flap of the card between thumb and fingers, which would inhibit screen-motion. Nor is there any design, in the lenticular lens version, offered to keep print and screen co-planar, so that even if the print could move freely, the hinged edge of the screen would lift up and away from the print as the card was opened, destroying co-planarity and putting the image out of focus.
Another drawback to existing devices is the lack of any type of adjustment for co-linearity between the lenticular image and the lenticules of its overlaying screen, which would become especially useful if an image became worn at its edge over time, or did not print exactly straight, or if a smaller lens-per-inch size were used, requiring more exact parallelism.
In addition, even for industrial, not to mention consumer use, the price of mastering lenticular images can be prohibitive. There is a need for a widely compatible, easy to use, low cost software, enabling mastering and printing of lenticular images with widely available computers and printers, as well as a file format containing pertinent information to a lenticular image, such as lenses per inch and number of compressed images, for downloading over electronic media.
Finally, there must be a means for reducing friction between print and screen, unless they are to be spaced apart, which requires extreme planar uniformity, whether flat or curved. Such uniformity is possible with a small image or where larger lenses, or those with longer focal lengths, are used, making their focal distance less critical. “Stiction”, that is, in this case, the tendency of the printed image to stick against the overlaying screen, until the friction between them breaks, will create an intermittent motion, rather than a smooth one, which is necessary for film-quality animation.